Study of Interactions between Amlodipine and Quercetin on Human Serum Albumin: Spectroscopic and Modeling Approaches

Covalent conjugation with polyphenol reduced the sensitization of walnut and ameliorated allergy by enhancing intestinal epithelial barrier in mice

In order to reduce the sensitization of walnut protein (WP), the effects of the interaction between WP and (-)-Epigallocatechin gallate (EGCG), quercetin, trans-ferulic acid, and resveratrol were investigated. Covalent and non-covalent conjugations were compared. The results suggested that covalent conjugation reduced the free amino acid content, sulfhydryl content, and surface hydrophobicity. When compared to non-covalent conjugation, covalent modification showed a lower IgE binding capacity, accompanied by changes in protein conformation. Moreover, animal experiments revealed that there were up-regulation of transforming growth factor-β, T-box expressed in t cells, and forkhead transcription factor Foxp3 mRNA expression, and down-regulation of IL-4, IL-17, GATA binding protein 3 and retinoid-related orphan nuclear receptor γt mRNA expression in the conjugate groups. These results suggested that covalent conjugation of polyphenols, especially EGCG, likely ameliorated allergy by promoting Th1/Th2 and Treg/Th17 balance and alleviating allergy-induced intestinal barrier damage, which might be a support in reducing the allergenicity of WP.

Antibacterial and Antihemolytic Activity of New Biomaterial Based on Glycyrrhizic Acid and Quercetin (GAQ) against Staphylococcus aureus

The goal of this study is to obtain and characterize the complex of quercetin with glycyrrhizic acid, which is known to serve as a drug delivery system. Quercetin is a flavonoid with a wide range of biological activities, including an antimicrobial effect. However, quercetin instability and low bioavailability that limits its use in medical practice makes it necessary to look for new nanoformulations of it. The formation of the GAQ complex (2:1) was confirmed by using UV and FT-IR spectroscopies. It was found that the GAQ exhibited antimicrobial and antihemolytical activities against S. aureus bacteria and its main virulent factor-α-hemolysin. The IC₅₀ value for the antihemolytical effect of GAQ was 1.923 ± 0.255 µg/mL. Using a fluorescence method, we also showed that the GAQ bound tightly to the toxin that appears to underlie its antihemolytic activity. In addition, another mechanism of the antihemolytic activity of the GAQ against α-hemolysin was shown, namely, its ability to increase the rigidity of the outer layer of the erythrocyte membrane and thus inhibit the incorporation of α-hemolysin into the target cells, increasing their resistance to the toxin. Both of these effects of GAQ were observed at concentrations below the MIC value for S. aureus growth, indicating the potential of the complex as an antivirulence agent.

The inhibitory effects of natural antioxidants on protein glycation as well as aggregation induced by methylglyoxal and underlying mechanisms

The non-enzymatic glycation of protein can result in the formation of advanced glycation end-products (AGEs), leading to the deposition of amyloid proteins, and it's essential for the pathogenesis of diabetes complications and amyloid diseases. Reactive dicarbonyl compounds, such as methylglyoxal (MGO), are one of the most reactive glycating agents. Therefore, it's crucially necessary to inhibit protein glycation and aggregation induced by MGO. In the present study, we aimed to systemically investigate the anti-glycation and anti-fibrillization activities of eight natural antioxidants, including apigenin, quercetin (Que), catechin, resveratrol (Res), and gallic acid (GA), L-ascorbic acid (L-AA), limonene, and β-carotene, during MGO-induced protein glycation and aggregation. Furthermore, the underlying mechanisms were clarified. The formation of AGEs and the degree of protein aggregation were characterized by optical detection, flow cytometry, and so on. The results demonstrated that eight selected natural antioxidants could inhibit glycation and protein aggregation induced by MGO via the synergy of scavenging free radicals, capturing MGO, and interacting with proteins, among which GA (300 μM) and Res (15 μM) had higher inhibition rates on both argpyrimidine (specific fluorescent AGEs, 17% and 22%, respectively) and protein amyloid aggregation (42% and 29%, respectively). These findings suggested that antioxidants could act as potential inhibitors of AGEs and glycation-induced protein aggregation, which were expected to become a new strategy for the prevention and treatment of diabetes and amyloid diseases. Besides, these inhibition mechanisms provided valuable insights into the design and development of candidate drugs for the prevention and treatment of AGEs and protein aggregation-related diseases.

Interaction Characterization of a Tyrosine Kinase Inhibitor Erlotinib with a Model Transport Protein in the Presence of Quercetin: A Drug-Protein and Drug-Drug Interaction Investigation Using Multi-Spectroscopic and Computational Approaches

The interaction between erlotinib (ERL) and bovine serum albumin (BSA) was studied in the presence of quercetin (QUR), a flavonoid with antioxidant properties. Ligands bind to the transport protein BSA resulting in competition between different ligands and displacing a bound ligand, resulting in higher plasma concentrations. Therefore, various spectroscopic experiments were conducted in addition to in silico studies to evaluate the interaction behavior of the BSA-ERL system in the presence and absence of QUR. The quenching curve and binding constants values suggest competition between QUR and ERL to bind to BSA. The binding constant for the BSA-ERL system decreased from 2.07 × 10⁴ to 0.02 × 10² in the presence of QUR. The interaction of ERL with BSA at Site II is ruled out based on the site marker studies. The suggested Site on BSA for interaction with ERL is Site I. Stability of the BSA-ERL system was established with molecular dynamic simulation studies for both Site I and Site III interaction. In addition, the analysis can significantly help evaluate the effect of various quercetin-containing foods and supplements during the ERL-treatment regimen. In vitro binding evaluation provides a cheaper alternative approach to investigate ligand-protein interaction before clinical studies.

Direct Visualization of Amlodipine Intervention into Living Cells by Means of Fluorescence Microscopy

Amlodipine, a unique long-lasting calcium channel antagonist and antihypertensive drug, has weak fluorescence in aqueous solutions. In the current paper, we show that direct visualization of amlodipine in live cells is possible due to the enhanced emission in cellular environment. We examined the impact of pH, polarity and viscosity of the environment as well as protein binding on the spectral properties of amlodipine in vitro, and used quantum chemical calculations for assessing the mechanism of fluorescence quenching in aqueous solutions. The confocal fluorescence microscopy shows that the drug readily penetrates the plasma membrane and accumulates in the intracellular vesicles. Visible emission and photostability of amlodipine allow confocal time-lapse imaging and the drug uptake monitoring.

Influence of antioxidant flavonoids quercetin and rutin on the in-vitro binding of neratinib to human serum albumin

This study was designed to examine the interaction of neratinib (NRB) with human serum albumin (HSA) in presence of flavonoids quercetin and rutin. Both quercetin and rutin can compete with NRB to bind to HSA and displace NRB from its binding site. The interaction mechanism was studied with several spectroscopic techniques and molecular docking. Static fluorescence quenching mechanism was observed on interaction of HSA with NRB. van der Waals force and hydrogen bond were involved in the HSA-NRB interaction as per the results of thermodynamic parameters. Further, the conformational changes were observed in the HSA on its interaction with NRB. Interaction of NRB with HSA in presence of quercetin and rutin resulted in changes in the binding constants of HSA-NRB suggesting some impact on the binding of NRB in the presence of flavonoids.

Effect of quercetin on the amiloride-bovine serum albumin interaction using spectroscopic methods, molecular docking and chemometric approaches

The effect of quercetin flavonoid (QUE), on the binding interaction of antihypertensive drug, amiloride (AMI) with bovine serum albumin (BSA) was investigated in this study. Spectroscopic methods such as steady-state, synchronous, three-dimensional fluorescence, and circular dichroism spectroscopy were employed to study the interaction. Fluorescence data were analyzed using the Stern-Volmer equation and a static quenching process was found to be involved in the formation of AMI-BSA and QUE-BSA complexes and were in good agreement with the thermodynamic study. The thermodynamic parameters illustrated that the process is spontaneous and enthalpy driven. Hydrophobicity is acting as the primary force in the binding interaction. Fluorescence spectral data were resolved using a multivariate curve resolution-alternating least squares method (MCR-ALS). Site marker and molecular docking studies confirmed the binding site of AMI on BSA, i.e. site II. The binding distance between amino acid of BSA and AMI was calculated and found to be 2.18 nm which indicated that energy transfer has occurred from an amino acid of BSA to AMI. The binding affinity of AMI to BSA was found to be reduced in the presence of QUE, which may lead to the poor distribution of AMI at the desired site.

Plasma Protein Binding of Herbal-Flavonoids to Human Serum Albumin and Their Anti-proliferative Activities

Herbal-flavonoids (HF) as polyphenolic secondary metabolites are taken in the daily diet to join in many metabolic processes in the human organism. Anti-proliferative activities and human serum albumin (HSA) binding capacities of herbal-flavonoids namely 7,5'-dimethoxyisoetin (HF1), homoorientin-6''-4-O-methyl-myo-inositol (HF2), (2R, 3R)-(+)-dihydrokaempferol-7,4'-dimethylether (HF3), eriodictyol-7,4'-dimethylether (HF4) and flavonoids isoorientin (HF5) and genkwanin (HF6) were investigated. Anti-proliferative activities were determined by the xCELLigence system by treatment with human prostate (PC3) and cervical cancer (HeLa) cells. The binding capacities were studied by two-dimensional (2D-FL) and three-dimensional (3D-FL) fluorescence spectroscopy. HeLa and PC3 cell lines were treated with flavonoids at 10, 50 and 100 μg/mL concentrations over a 48 hour period. Stable anti-proliferative efficacy plots were obtained for tested flavonoids. From the flavonoids, HF3 and HF4 showed the strongest anti-proliferative effect against PC3 and HeLa cell line. HF1 and HF2 exhibited the strongest binding capacity to the HSA corresponding to Kb values of 3.81 x 104 M-1 and 6.00 x 104 M-1, respectively. The studies revealed that the flavonoids form the basis of in vivo preclinical studies as important nutraceuticals of the daily diet, as well as modelled in medical and pharmacological applications.

Investigation of complexation of amlodipine with lysozyme and its effect on lysozyme crystal growth

Lysozyme (LYZ) is a model protein frequently employed to study interaction with drugs and to understand the crystallization process of protein due to its small size and rapid crystallization behavior. Studies related to drug interaction and complexation with proteins will be significantly benefited if a suitable drug-lysozyme crystal is available. This can further aid in the understanding of the mechanism of nucleation, growth and the formation of drug-lysozyme complex. In the present study, amlodipine (AMLD) complexation with LYZ has been monitored, along with its effect on lysozyme crystallization. Different spectroscopic methods have been employed to monitor the nature of complexation, binding mode and changes in helix after interaction with AMLD. The absorbance and fluorescence spectroscopic measurement indicated the probability of a ground state complex between LYZ and AMLD. Further, the temperature dependent fluorescence studies showed an increase in binding constant with temperature, suggesting the static quenching mechanism involved in complex formation due to hydrophobic interactions. CD, FTIR, DLS and DSC techniques confirm the probability of changes in the tertiary structure of protein. Molecular docking was applied to investigate the interaction of amino acid residues of LYZ with AMLD. It was found that the complex formation is spontaneous and the ΔG value obtained (-21. 76 kJ/mol) very well matched with temperature dependent fluorescence study (-24.91 kJ/mol). Crystallization of LYZ was performed with different concentration ranges of AMLD to get a clear picture of its interference on the process. The time required for crystallization of AMLD-LYZ complex and the observed structure of crystal indicates that AMLD influences lysozyme crystallization process by changing the nature of nucleation and rate of crystal growth.

Analysis of Binding Interactions of Ramipril and Quercetin on Human Serum Albumin: A Novel Method in Affinity Evaluation

The aim of this study was to analyze the binding interactions between a common antihypertensive drug (ramipril, R) and the widely distributed plant flavonoid quercetin (Q), in the presence of human serum albumin (HSA). From the observed fluorescence spectra of the (HSA + R) system we can assume that ramipril is also one of the Site 3 ligands—similar to fusidic acid—the binding of which has been proven by RTG crystallography. Our claim is supported by near-UV CD spectroscopy, microscale themophoresis and molecular modeling. The presence of R slightly inhibited the subsequent binding of Q to HSA and, on the contrary, the pre-incubation of HSA with Q caused a stronger binding of R, most likely due to allosteric interactions. At high concentrations, R is also able to displace Q from its binding site. The dissociation constant K_D for the binding of R is more than hundredfold larger than for Q, which means that R is a very weak binder to HSA. The knowledge of qualitative and quantitative parameters of R, as well as the methods used in this study, are important for future research into HSA binding. This study shows the importance of implementing other methods for K_D determination. Microscale thermophoresis has proved to be a novel, practical and accurate method for K_D determination on HSA, especially in cases when fluorescence spectroscopy is unable to produce usable results.

Probing the interaction between levamlodipine and hemoglobin based on spectroscopic and molecular docking methods

In recent years, levamlodipine (LAML) has been widely used as a common drug for the treatment of hypertension. However, no reports exist that focus on the binding process of LAML with the transport proteins present in blood circulation. Here, several spectroscopy techniques, molecular docking and a molecular dynamics simulation were employed to comprehensively analyze the mechanism underlying the interaction between bovine hemoglobin (BHb) and LAML, as well as the effect of other drugs on the BHb-LAML system. The results indicated that a stable BHb-LAML complex was formed and that the binding site for LAML was located at β-37 tryptophan in the central cavity of BHb. Van der Waals force and hydrogen bonds played major roles in this binding process, and the number of binding sites (n) in the binary system was approximately equal to 1. Multiple spectroscopy experiments (FT-IR and three-dimensional fluorescence spectrometry) and a dynamics simulation revealed that LAML could induce a conformational in BHb and that the microenvironment of Trp/Tyr changed. Interestingly, the values of the binding constant between LAML and BHb significantly increased due to the effect of rofecoxib, propranolol and enalapril. Meanwhile, these drugs did not produce synergistic or negative synergistic effects on the LAML binding with BHb. These results provide new insight into the transport mechanisms for LAML in the human body.

The interaction of silica nanoparticles with catalase and human mesenchymal stem cells: biophysical, theoretical and cellular studies

Aim

Nanoparticles (NPs) have been receiving potential interests in protein delivery and cell therapy. As a matter of fact, NPs may be used as great candidates in promoting cell therapy by catalase (CAT) delivery into high oxidative stress tissues. However, for using NPs like SiO₂ as carriers, the interaction of NPs with proteins and mesenchymal stem cells (MSCs) should be explored in advance.

Methods

In the present study, the interaction of SiO₂ NPs with CAT and human MSCs (hMSCs) was explored by various spectroscopic methods (fluorescence, circular dichroism (CD), UV-visible), molecular docking and dynamics studies, and cellular (MTT, cellular morphology, cellular uptake, lactate dehydrogenase, ROS, caspase-3, flow cytometry) assays.

Results

Fluorescence study displayed that both dynamic and static quenching mechanisms and hydrophobic interactions are involved in the spontaneous interaction of SiO₂ NPs with CAT. CD spectra indicated that native structure of CAT remains stable after interaction with SiO₂ NPs. UV-visible study also revealed that the kinetic parameters of CAT such as Km, Vmax, Kcat, and enzyme efficiency were not changed after the addition of SiO₂ NPs. Molecular docking and dynamics studies showed that Si and SiO₂ clusters interact with hydrophobic residues of CAT and SiO₂ cluster causes minor changes in the CAT structure at a total simulation time of 200 ps. Cellular assays depicted that SiO₂ NPs induce significant cell mortality, change in cellular morphology, cellular internalization, ROS elevation, and apoptosis in hMSCs at higher concentration than 100 µg/mL (170 µM).

Conclusion

The current results suggest that low concentrations of SiO₂ NPs induce no substantial change or mortality against CAT and hMSCs, and potentially useful carriers in CAT delivery to hMSC.